Are beer bellies a real thing? Do social drinkers really carry around an extra five pounds of weight?

I have avoided investigating the answers to this question for all my adult life — and all my years as a health reporter. Call it denial by someone who likes her wine.

Recently I learned that the caloric content of alcohol is higher (seven calories per gram) than that of proteins and sugars (both four calories per gram), and nearly as much as fats (nine calories).

That sounded very worrying, I’ll admit. But remember that for managing weight, a more important number is the total number of calories in your beer (about 150 calories in a 12-ounce serving of regular brew, a reminder that there’s more to a drink than the alcohol) or your glass of red wine (125 calories in a five-ounce serving). A sugar-heavy 12-ounce cola also carries 150 calories.

And as far as common wisdom on drinking and weight gain goes, I am here to report, the science is murky.

(Larry Crowe/AP)

For starters, epidemiological studies in large populations frequently show that moderate drinkers tend to gain less weight over time than teetotalers, says David Hanson, an alcohol expert at the State University of New York at Potsdam. “There’s every reason to believe people who drink alcohol will gain weight,” he says, “but they don’t.”

Women who drink moderately — that’s defined by the National Institute on Alcohol Abuse and Alcoholismas one drink per day for women, two for men — seem to do the best in terms of the dreaded weight gain in middle age. Looking at body mass index — a gauge of fat calculated by weight and height — a 1997 study found that women added an average 1.4 to their BMI in a 10-year period; but beer-drinking and wine-drinking women generally lost as much as 0.4 BMI units. For a 5-foot-4-inch woman, that’s the equivalent to gaining 8 pounds or losing 2 pounds.

Rosalind Breslow, an NIAAA researcher, studied survey data from 45,896 adults to see if patterns of drinking made a difference in weight gain over time. Rather than looking at average alcohol consumption over a period of time, her team measured drinking days per month and number of drinks on those days. She found greater BMIs in people who reported higher consumption on the days they chose to drink; for instance, men who had four or more drinks on days they drank had BMIs one unit higher than those who usually limited themselves to a single drink. For a 5-foot-9-inch man, that’s a 7-pound gain. However, those who drank several days a week had lower BMIs than those who drank only occasionally — less than once a month.

“When you put it together, people who were heaviest drank a big amount with the lowest frequency,” Breslow says. “The people who were the leanest drank small quantities more frequently.”

This means that people who really let loose on the weekends, drinking-wise, may be at more risk for weight gain than people who have a single glass of wine with dinner most nights.

Some diet plans advise you to avoid alcohol if you want to lose weight. Weight Watchers doesn’t ban alcohol, but it assigns points to alcoholic drinks to make sure dieters are accounting for those calories. “Otherwise, we’re totally neutral on whether you drink one or two glasses of wine,” says Gary Foster, the chief scientific officer at Weight Watchers. “You spend your points the way you want.”

Still, Foster warns, alcohol has a disinhibiting effect on behavior. You might go into a holiday party with the plan to stick to fruit and vegetables, but after a drink or two, you may throw that plan away and dive into the fried foods. “You wouldn’t make your best business decisions after two glasses of wine,” Foster says. “You won’t make your best eating decisions, either.”

There’s also the question of whether alcohol stimulates appetite. In laboratory studies, people primed with a drink will generally eat more than they do when they don’t have a drink. This may be the disinhibiting effect Foster describes. Even if people eat the same amount after a cocktail as they do without one, they would still be taking in more calories — the drink plus the food. There’s evidence that the body doesn’t notice liquid calories the same way as it does those from solid food, so overall caloric intake goes up with alcoholic drinks, as it does in meals with sugary sodas.

Most of us don’t drink under laboratory conditions however. Breslow did a study last year where she sifted through six years of survey data to find 1,864 people who had reported a day’s worth of eating and drinking on two occasions — one day with alcohol and one without.

Calorie intake on drinking days was more than on non-drinking days — by 433 calories for men and 299 calories for women. The researchers looked at what kinds of food people ate on the two days and found that men ate more white potatoes, meat and fats on drinking days. “That sounds suspiciously like hamburger and fries,” Breslow says, although she cautions that the researchers didn’t actually collect that level of detail. They also ate less fruit and drank less milk.

The study showed that in real-life situations, people consumed more calories and ate less healthful food on days they drank than on days they didn’t.

So what’s the takeaway here? If you’re a social drinker, you need not necessarily gain weight. But you might examine your habits; for example, when you indulge in drink, do you also indulge in junk food?

Breslow, who is also trained as a dietitian, leaves me with this advice: This holiday season, think before you eat. Plan before you go to a party. And watch out for portion size — for both food and drink. “You can fit several drinks into a large glass, so you could end up drinking more than you think,” she says.